The present invention relates to the art of chewing gum base compositions, and, in particular, to gum base compositions which include an elastomer and a resin component prepared without the need for certain undesirable components.
Chewing gums available today generally contain a water-insoluble or base portion and a water-soluble flavor portion which is dissipated over a period of time during mastication of the gum in the oral cavity. The base portion can include a natural or a synthetic elastomer, and, optionally, a resin component and a texturizing component for achieving a particular perceived effect by the consumer.
The present invention is particularly concerned with those gum base compositions in which there are both an elastomeric portion as well as a resin component which can be made to be compatible in combination without the need for certain undesirable ingredients heretofore generally considered necessary.
The elastomer component can, in accordance with the present state of the art, include synthetic elastomers, natural elastomers, or combinations thereof. This element generally provides the insoluble cud with resiliency to recover from deformation caused during chewing. The resin component, which is also a polymeric material, provides the insoluble cud portion of the gum with other desirable characteristics such as film forming capabilities, and inherent strength for unbroken deformation under chewing forces, i.e., "lay-flat" quality, etc.
In order for the overall cud containing both an elastomeric portion and a resin component to retain the desired characteristics of the combination, the inherent cohesivity of each of the individual components must be overcome or dissociated to some extent in order to open up the structure sufficiently to be compatible for mixing. Only when the two components are "opened up" sufficiently to be miscible to some extent with each other, can a satisfactory base portion be provided for addition of desired texturizing agents and eventually chewing gum composition ingredients, e.g., sugar, flavoring, etc.
Thus, in order to prepare a high-grade gum base, it is necessary to effect compatibilization of an elastomer and the resin component when the two are used in combination. In the case of high molecular weight resins, this can be a particularly difficult problem, in view of the intensity of the inherent strength of the inter-molecular attractive forces or inter-molecular interaction.
In the past, it has been generally considered necessary to include rosin esters, hydrogenated rosin esters, polymerized rosin esters and unhomogenized rosin esters, and terpene resins to compatibilize the elastomeric component with the resin component especially high molecular weight resin such as high molecular weight polyvinylacetate, e.g., having a molecular weight of greater than about 20,000.
Although the use of these esters and ester derivatives, help to compatibilize otherwise generally immiscible gum components, there are several drawbacks which would encourage one to refrain from using such ester gums. In particular, ester gums have unpleasant taste and odor and are characteristically rigid, very hard, brittle, nonchewable, and require significant amount of energy as well as the addition of extensive amounts of softeners, fillers, etc., in order to achieve proper texturization. Thus, even though the gum can be pliable and elastic at the beginning of the chewing or mastication period, it can quickly become excessively pliable and sticky in the mouth, lose its elasticity, and develop an unpleasant chewing sensation. Furthermore, cracks can develop in the gum during storage which can cause shedding.
Similarly, elastomer solvents used to compatibilize elastomer components with resins have included terpene resins such as polymers of beta pinene, and beta-pinene. Other problems are incurred by use of the terpene solvents, similar to those problems incurred by use of rosin esters and derivatives thereof.
Efforts in the past to eliminate the need for wood rosin esters and terpenes, have included polymerizing the monomer unit of a resin such as vinyl acetate and/or vinyl propionate in the presence of a hydrogenated petroleum resin alone or in mixture with a hydrogenated petroleum resin with known chewing gum base additives and/or known natural resins for chewing gum bases. This is disclosed in Japanese Patent Public Disclosure No. 49-205,10 (1974). Other efforts have included the use of comparatively expensive compatibilization components such as glycerol triacetate, and acetylated monoglyceride, combinations thereof, etc. For example, U.S. Pat. No. 4,452,820 to D'Amelia, et al. discloses a single phase formulated homogeneous gum base which contains a plasticized elastomer and a plasticized resin in the absence of ester gum. In the case of the D'Amelia, et al. '820 disclosure, a styrene butadiene elastomer is plasticized with a plasticizer selected from one of butyl stearate, butyl oleate, glycerol trioleate, oleic acid, or mixtures thereof, while the resin component is plasticized with a plasticizer selected from the group consisting of glycerol triacetate, glycerol tributyrate, triethyl citrate, acetylated monoglyceride, etc. and combinations thereof. In the case of the process disclosed in the Japanese reference, it is required to copolymerize the components, and in the case of the D'Amelia '820 disclosure, it is necessary to provide a plasticizer for each of the components, one of which is a rather expensive plasticization component.
U.S. Pat. No. 4,525,363 to D'Amelia, et al. discloses a variety of polymers which plasticize both the resin and the elastomer components. The polymers are of the polymeric resin type materials and include, for example, acrylates, acetates, butylenes and silicones. The elastomer may be a styrene butadiene whereas the resin may be a polyvinyl acetate. The D'Amelia, et al. '363 reference also discloses the optional inclusion of waxes having a relatively low melting point which may be present in an amount of from about 0% to about 18% so as to reduce the tackiness of the final gum composition.
U.S. Pat. No. 2,284,804 to De Angelis discloses polybutene chewing gum base compositions which include the use of "substantial quantities of wax at least equal to the amount of polybutene present." (Col. 2, Lines 28-30). The resin component of the base disclosed, however, is indiscriminately chosen from hydrogenated synthetic and hydrogenated natural resins and ester gums. (Col. 2, Lines 42-45.).
The use of waxes in a gum base has also been contemplated. U.S. Pat. No. 2,137,746 to Wilson discloses chewing gum bases which include small proportions of paraffin waxes having melting points in the range of about 160.degree. F. to about 185.degree. F. in combination with natural elastomers or in combination with latex elastomers and ester gums so as to improve the smoothness of the gum formulations while retaining the other desirable properties of the springiness and roundness of the cud. The Wilson disclosure, however, fails to suggest a gum base having compatibilized synthetic elastomers.
Similarly, in U.S. Pat. No. 3,984,574 to Comollo an attempt has been made to reduce the need for rosin derivatives, with polyvinyl acetate and polyterpenes in order to reduce the tackiness associated with such bases. In order to do so, Comollo requires the use of polyisobutylene in combination with polyvinyl acetate and hydrogenated or partially hydrogenated vegetable oils or fats in an amount of 5-50%, and filler in an amount of 5-40% in order to allegedly achieve an adhesive or non-tacky base. The Comollo '574 disclosure requires the use of vegetable oils and fats and mineral adjuvants as fillers to achieve the desired result. Thus, it is an object of the present invention to provide a gum base composition which includes both an elastomer and a resin in the absence of rosin esters.
It is a further object to provide a gum base as described above which does not require the use of terpene softeners.
A further object of the present invention is to provide a gum base without the need for ester and terpene softeners by use of a inexpensive compatibilization component.
Yet a further object of the present invention is to provide a gum base in which a chewing gum composition can be prepared in a continuous process without the requirement for aging, cooling, etc.
Other objects will become apparent to the skilled practitioner in view of the disclosure as set forth below.